In the prior art industrial buildings such as building systems structures of the type that include metal purlins supported on inclined metal rafters and sheet metal roofing panels attached to the purlins, the spread of fires usually is difficult to control when the fire reaches the roof because of the expanse of open space beneath the roof structure. This generally is due to the effect of the movement of heated gases and flames through the open space beneath the roof structure of the building. Once the fire has spread to the roof of the building, the fire usually is already out of control and it becomes likely that the building will be destroyed by the fire.
Fire resistant insulation material has been developed and installed in industrial buildings to help in the control of the spread of fires through such buildings. Such insulation materials typically have been used in conjunction with a poured concrete deck over which the fire resistant material is placed, with a built up roof structure on top of the fire resistant material and the concrete deck. Such an arrangement typically provides effective protection against the spread of fire and gases through a concrete roof.
However, such fire resistant materials are not nearly as effective when used in building systems structures which do not use a concrete slab-based roof structure. The omission of the concrete slab apparently reduces the effectiveness of the fire resistant material to resist the spread of fire and hot gases through the roof structure of the building. Further, panels formed from such fire resistant materials often have an irregular shape, making it difficult to form a tight seal between adjacent panels.
The suspended insulation systems taught by the prior art for use in the roof structures of building systems structures typically suspend fire resistant panels on top of metal cross pieces suspended from the purlins of the roof structure by metal hangers. Such an abundance of metal fixtures hanging below the fire resistant panels of the roof structure provides direct heat conductivity and heat absorption through the roof structure. Thus, the effectiveness of the fire resistant panels to retard the spread of flames and combustible gases is decreased by the significant exposure of metal to metal contact of the prior art systems.
Consequently, to achieve a standard one hour fire rating for the roof structure of building systems structures it has been necessary to use a substantially greater amount of fire resistant material in the roof structure, which increases the cost of the roof structure. When only one layer of fire resistant material is used in the roof structure as generally taught by the prior art, the single layer of material must be able to withstand the entire amount of temperature gradient from the hot side to the cool side of the roof structure. This requires a relatively large thickness of the insulation material, which results in the inconvenience and expense of installing heavier, thicker, expensive material. An alternative has been to simply not build a building systems structure but to build another type of building. As a result, it has been generally believed impractical to erect a building systems structure in areas where fire code regulations require roof structures to have at least a one hour fire resistance rating.
Accordingly, it can be seen that it would be desirable to provide an insulated roof structure for building systems structures and a method of installing such a roof structure which provides an effective and inexpensive flame and gas seal to retard the spread of flames and hot gases from a fire through the roof structure of the building.